The invention relates to steam generators having wet scrubbers and in particular to the reheating of gases leaving the wet scrubbers.
The gases leaving wet scrubbers are saturated with water because of the scrubbing, and normally also include some entrained water carry over. This moisture leads to corrosion of downstream equipment and rainout in the immediate plant area. It also creates a visible and relatively dense plume in the gases leaving the stack. It is, therefore, customary to reheat these gases immediately after scrubbing for the purposes of avoiding such corrosion, rainout, and to increase the plume buoyancy.
The primary sources of heat for flue gas reheating have been extraction steam from the turbine, or hot water from the feedwater cycle. The use of extraction steam reduces the total kilowatt output of the station, and the use of water from the feedwater cycle requires that the feedwater cycle be oversized to supply this hot water. Since the feedwater is heated by extraction steam, this also reduces the kilowatt output of the station.